Optical inspection apparatus, processing device, optical inspection method, and non-transitory storage medium storing optical inspection program

ABSTRACT

According to an embodiment, an optical inspection apparatus includes an imaging portion, a first wavelength selection portion, an illumination portion, and a second wavelength selection portion. The imaging portion includes an image sensor configured to capture a subject by light from the subject. The first wavelength selection portion is provided on an optical axis of the imaging portion and is configured to selectively pass a plurality of light components of predetermined wavelengths. The illumination portion is configured to illuminate the subject. The second wavelength selection portion is provided on an optical axis of the illumination portion and is configured to pass the plurality of light components of the predetermined wavelengths complementarily to the first wavelength selection portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromJapanese Patent Application No. 2022-045287, filed Mar. 22, 2022, theentire contents of all of which are incorporated herein by reference.

FIELD

Embodiments described herein relate generally to an optical inspectionapparatus, a processing device, an optical inspection method, and anon-transitory storage medium storing an optical inspection program.

BACKGROUND

In various industries, surface measurement of an object in a noncontactstate is important. As a conventional method, there exists a method ofacquiring BRDF information capable of describing the surface state of anobject surface by associating a light beam with a color in eachdirection.

BRIEF DESCRIPTION OF THE DRAWING (S)

FIG. 1 is a schematic sectional view showing the operation principle ofan optical inspection apparatus according to the first embodiment.

FIG. 2 is a schematic view showing the first wavelength selectionportion of the optical inspection apparatus shown in FIG. 1 .

FIG. 3 is a schematic view showing the second wavelength selectionportion of the optical inspection apparatus shown in FIG. 1 .

FIG. 4 is a schematic sectional view showing the operation principle ofthe optical inspection apparatus according to the first embodiment.

FIG. 5 is a schematic flowchart showing the processing procedure of theprocessing device of the optical inspection apparatus shown in FIGS. 1,2, 3, and 4 .

FIG. 6 is a schematic view showing a modification of the firstwavelength selection portion (and the second wavelength selectionportion) used in the optical inspection apparatus according to the firstembodiment.

FIG. 7 is a schematic sectional view showing the operation principlewhen performing optical inspection using the first wavelength selectionportion (and the second wavelength selection portion) shown in FIG. 6 .

FIG. 8 is a schematic view showing an example of the first wavelengthselection portion (and the second wavelength selection portion) used inthe optical inspection apparatus according to the first embodiment.

FIG. 9 is a schematic view showing an example of the first wavelengthselection portion (and the second wavelength selection portion) used inthe optical inspection apparatus according to the first embodiment.

FIG. 10 is a schematic view showing an example of the first wavelengthselection portion (and the second wavelength selection portion) used inthe optical inspection apparatus according to the first embodiment.

FIG. 11 is a schematic view showing an example of the first wavelengthselection portion (and the second wavelength selection portion) used inthe optical inspection apparatus according to the first embodiment.

FIG. 12 is a schematic view showing an example of the first wavelengthselection portion (and the second wavelength selection portion) used inthe optical inspection apparatus according to the first embodiment.

FIG. 13 is a schematic sectional view showing the operation principle ofan optical inspection apparatus according to the second embodiment.

FIG. 14 is a schematic sectional view showing the operation principle ofan optical inspection apparatus according to the third embodiment.

FIG. 15 is a schematic view showing the second wavelength selectionportion of the optical inspection apparatus shown in FIG. 14 .

FIG. 16 is a schematic sectional view showing the operation principle ofan optical inspection apparatus according to the fourth embodiment.

FIG. 17 is a schematic sectional view showing the operation principle ofan optical inspection apparatus according to the fifth embodiment.

DETAILED DESCRIPTION

It is an object of an embodiment to provide an optical inspectionapparatus capable of increasing the accuracy of optical inspection of asurface of a subject, a processing device, an optical inspection method,and a non-transitory storage medium storing an optical inspectionprogram.

According to the embodiment, an optical inspection apparatus includes animaging portion, a first wavelength selection portion, an illuminationportion, and a second wavelength selection portion. The imaging portionincludes an image sensor configured to capture a subject by light fromthe subject. The first wavelength selection portion is provided on anoptical axis of the imaging portion and is configured to selectivelypass a plurality of light components of predetermined wavelengths. Theillumination portion is configured to illuminate the subject. The secondwavelength selection portion is provided on an optical axis of theillumination portion and is configured to pass the plurality of lightcomponents of the predetermined wavelengths complementarily to the firstwavelength selection portion.

Embodiments will now be described with reference to the accompanyingdrawings. The drawings are schematic or conceptual, and the relationshipbetween the thickness and the width of each part, the size ratio betweenportions, and the like do not always match the reality. Also, even sameportions may be illustrated in different sizes or ratios depending onthe drawing. In the present specification and the drawings, the sameelements as described above in already explained drawings are denoted bythe same reference numerals, and a detailed description thereof willappropriately be omitted.

In this specification, light is a kind of electromagnetic wave, andincludes X-rays, ultraviolet rays, visible light, infrared rays,microwaves, and the like. In this embodiment, it is assumed that thelight is visible light, and for example, the wavelength is in a regionof 450 nm to 700 nm.

First Embodiment

An optical inspection apparatus 10 according to this embodiment will bedescribed in detail with reference to FIGS. 1 to 5 .

FIG. 1 is a schematic sectional view of the optical inspection apparatus10 according to this embodiment.

The optical inspection apparatus 10 according to this embodimentincludes an imaging portion 12 and an illumination portion 14.

The imaging portion 12 includes an imaging optical element (firstimaging optical element) 22, and an image sensor (to be also referred toas a sensor) 26 configured to capture a subject S by light from thesubject S. The imaging portion 12 is provided with a first wavelengthselection portion 24 that selectively passes a plurality of lightcomponents of predetermined wavelengths. The illumination portion 14includes a light source 32, and an illumination lens (second imagingoptical element) 36. The illumination portion 14 is provided with asecond wavelength selection portion 34 that selectively passes aplurality of light components of predetermined wavelengths.

The imaging optical element 22 is, for example, an imaging lens. In FIG.1 , the imaging lens is schematically drawn and represented by one lensbut may be a lens set formed by a plurality of lenses. Alternatively,the imaging optical element 22 may be a concave mirror, a convex mirror,or a combination thereof. That is, any optical element having a functionof collecting, to a conjugate image point, a light beam group exitingfrom one point of an object, that is, an object point can be used as theimaging optical element 22. Collecting (condensing) a light beam groupexiting from an object point on an object surface to an image point bythe imaging optical element is called imaging. This is also expressed astransferring an object point to an image point (the conjugate point ofthe object point). In addition, the aggregate plane of conjugate pointsto which a light beam group exiting from a sufficiently apart objectpoint is transferred by the imaging optical element will be referred toas the focal plane of the imaging optical element. A line that isperpendicular to the focal plane and passes through the center of theimaging element is defined as an optical axis L1 of the imaging portion12. At this time, the conjugate image point of the object pointtransferred by the light beam will be referred to as a focal point.

The first wavelength selection portion 24 is arranged on the opticalaxis L1. The first wavelength selection portion 24 is arranged on ornear a first focal plane F1 of the imaging optical element 22. When thefirst wavelength selection portion 24 is arranged on the focal plane F1of the imaging optical element 22, coloring according to the directionof the light beam is possible (see Hiroshi Ohno and Takahiro Kamikawa,“One-shot BRDF imaging system to obtain surface properties,” OpticalReview volume 28, pages 655-661 (2021).).

The first wavelength selection portion 24 includes at least twowavelength selection regions 24 a and 24 b. The two wavelength selectionregions are the (1-1)th wavelength selection region 24 a and the (1-2)thwavelength selection region 24 b. The (1-2)th wavelength selectionregion 24 b passes a light beam having a first wavelength. Here, passinga light beam means making the light beam headed from the object point tothe image point by transmission or reflection. In this embodiment, it isassumed that the (1-2)th wavelength selection region 24 b passes thelight beam of the first wavelength. On the other hand, the (1-2)thwavelength selection region 24 b substantially shields a light beam of asecond wavelength. Here, shielding means not to cause the light beam topass. That is, this means not to make the light beam headed from theobject point to the image point. However, shielding also includes a casewhere the intensity of the light beam is greatly decreased, and a smallnumber of remaining components are passed. The (1-1)th wavelengthselection region 24 a passes the light beam having the secondwavelength. In this embodiment, it is assumed that the (1-1)thwavelength selection region 24 a passes the light beam of the secondwavelength. On the other hand, the (1-1)th wavelength selection region24 a substantially shields the light beam of the first wavelength. Forexample, the first wavelength is red light with a wavelength of 650 nm,and the second wavelength is blue light with a wavelength of 450 nm.However, the present invention is not limited to this, and anywavelengths can be used.

The image sensor (to be also referred to as a sensor in short) 26 cancapture the subject S by light from the subject S. The image sensor 26includes one or more pixels, and each pixel can receive light beams ofat least two different wavelengths, that is, the light beam of the firstwavelength and the light beam of the second wavelength. However, the twodifferent wavelengths need not always be identifiable. That is, thesensor 26 can be a monochrome sensor. A plane including the region wherethe sensor 26 is arranged is the image plane of the imaging opticalelement. The sensor 26 can be either an area sensor or a line sensor.The area sensor is a sensor in which pixels are arrayed in an area onthe same surface. The line sensor is a sensor in which pixels arelinearly arrayed. Each pixel may include three color channels of R, G,and B. However, the sensor may be a monochrome sensor with one channel.In this embodiment, the sensor 26 is an area sensor in which each pixelcan receive two, red and blue light components. That is, each pixel canreceive blue light with a wavelength of 450 nm and red light with awavelength of 650 nm.

As the light source 32, for example, a surface emission type LED isused. However, the light source 32 is not limited to this, and any lightsource that emits light can be used. The light source 32 may be, forexample, a surface emission type OLED, a xenon lamp or a halogen lampcombined with a diffusion plate, an X-ray source, or an infrared raysource.

The second wavelength selection portion 34 is arranged on an opticalaxis L2. The second wavelength selection portion 34 includes at leasttwo wavelength selection regions 34 a and 34 b. The two wavelengthselection regions are the (2-1)th wavelength selection region 34 a andthe (2-2)th wavelength selection region 34 b. The (2-1)th wavelengthselection region 34 a passes a light beam having a first wavelength.Here, passing a light beam means making the light beam headed from theobject point to the image point by transmission or reflection. On theother hand, the (2-1)th wavelength selection region 34 a substantiallyshields a light beam of a second wavelength. Here, shielding means notto cause the light beam to pass. That is, this means not to make thelight beam headed from the object point to the image point. The (2-2)thwavelength selection region 34 b passes a wavelength spectrum includingthe light beam of the second wavelength. On the other hand, the (2-2)thwavelength selection region 34 b substantially shields the light beam ofthe first wavelength.

The illumination lens 36 is, for example, an imaging lens. In FIG. 1 ,the illumination lens 36 is schematically drawn and represented by onelens but may be a lens set formed by a plurality of lenses.Alternatively, the illumination lens 36 may be a concave mirror, aconvex mirror, or a combination thereof. That is, any optical elementhaving a function of collecting, to a conjugate image point, a lightbeam group exiting from one point of an object, that is, an object pointcan be used as the illumination lens 36. Collecting (condensing) a lightbeam group exiting from an object point on an object surface to an imagepoint by the illumination lens 36 is called imaging. This is alsoexpressed as transferring an object point to an image point (theconjugate point of the object point). In addition, the aggregate planeof conjugate points to which a light beam group exiting from asufficiently apart object point is transferred by the illumination lens36 will be referred to as the focal plane of the illumination lens(imaging optical element) 36. A line that is perpendicular to the focalplane and passes through the center of the illumination lens 36 isdefined as the optical axis L2 of the illumination portion 14. At thistime, the conjugate image point of the object point transferred by thelight beam will be referred to as a focal point. The second wavelengthselection portion 34 is arranged on or near a second focal plane F2 ofthe illumination lens 36.

When the second wavelength selection portion 34 is thus arranged on thefocal plane F2 of the illumination lens 36, light can be colored(extracted) in accordance with the direction of the light beam (seeHiroshi Ohno and Takahiro Kamikawa, “One-shot BRDF imaging system toobtain surface properties,” Optical Review volume 28, pages 655-661(2021).). That is, when the light from the light source 32 passesthrough the second wavelength selection portion 34, the wavelengthspectrum of the light changes in accordance with the direction of thelight beam.

In this embodiment, light from a light emitting point E of the lightsource 32 passes through the second wavelength selection portion 34,propagates along the optical axis L2 of the illumination lens 36, andforms an image at an object point O on the surface of the subject S viaa beam splitter 38. Here, it can be considered that the optical axis L2of the illumination portion 14 is bent via the beam splitter 38.

The distribution of directions of reflected light beams from the objectpoint O on the surface of the object S can be represented by adistribution function called BRDF (Bidirectional ReflectanceDistribution Function). The BRDF changes depending on the surfaceproperties/shape in general. That is, the BRDF changes depending on thesurface state of an object surface. For example, if the surface isrough, reflected light spreads in various directions. Hence, the BRDFrepresents a wide distribution. That is, the reflected light exists in awide angle. On the other hand, if the surface is a mirror surface,reflected light includes almost only specular reflection components, andthe BRDF represents a narrow distribution. As described above, the BRDFreflects the surface properties/shape of the object surface. Here, thesurface properties/shape may be a surface roughness, fine unevenness ona micron order, tilt of the surface, or distortion or the like. That is,any properties concerning the height distribution of the surface can beused. If the surface properties/shape is formed by a fine structure, thetypical structure scale can be any scale such as a nano-scale,micron-scale, or a milli-scale.

The first wavelength selection portion 24 shown in FIG. 2 and the secondwavelength selection portion 34 shown in FIG. 3 have complementarity.That is, these have at least a correlation relationship. Here, if thefirst wavelength selection portion 24 and the second wavelengthselection portion 34 have complementarity, these have the following twofeatures.

As the first feature, the first wavelength selection portion 24 and thesecond wavelength selection portion 34 have similar shapes. Here, thewhole regions of the first wavelength selection portion 24 and thesecond wavelength selection portion 34 need not be similar to eachother. For example, the first wavelength selection portion 24 and thesecond wavelength selection portion 34 can have any whole size or outeredge shape. That is, it is only necessary that in the first wavelengthselection portion 24 and the second wavelength selection portion 34, theregions where the light beams used for imaging pass are similar to eachother.

Here, a sectional view of the first wavelength selection portion 24 inFIG. 1 corresponds to the upper view of FIG. 2 . Also, a cross sectionof the first wavelength selection portion 24 along a plane orthogonal tothe optical axis L1 corresponds to the lower view of FIG. 2 . Asectional view of the second wavelength selection portion 34 in FIG. 1corresponds to the right view of FIG. 3 . Also, a cross section of thesecond wavelength selection portion 34 along a plane orthogonal to theoptical axis L2 corresponds to the left view of FIG. 3 . The sectionalview of the first wavelength selection portion 24 along the planeorthogonal to the optical axis L1 and the sectional view of the secondwavelength selection portion 34 along the plane orthogonal to theoptical axis L2 have similar shapes. That is, the (1-1)th wavelengthselection region 24 a of the first wavelength selection portion 24 andthe (2-1)th wavelength selection region 34 a of the second wavelengthselection portion 34 have similar shapes. Similarly, the (1-2)thwavelength selection region 24 b of the first wavelength selectionportion 24 and the (2-2)th wavelength selection region 34 b of thesecond wavelength selection portion 34 have similar shapes. However,even in or near the regions where the light beams used for imaging pass,the first wavelength selection portion 24 and the second wavelengthselection portion 34 may have shapes different from each other iflocally. This will be explained in an embodiment to be described later(see

FIG. 14 ). For example, the second wavelength selection portion 34 mayinclude a wavelength shielding portion 35. Also, the first wavelengthselection portion 24 may include a similar shielding portion in additionto or in place of the wavelength shielding portion 35.

As the second feature, the wavelength selection regions 24 a and 24 b ofthe first wavelength selection portion 24 and the wavelength selectionregions 34 a and 34 b of the second wavelength selection portion 34 havea relationship complementary to the passing wavelength regions. That is,these have a correlation relationship with each other at least for thepassing wavelength regions. The wavelength regions of the light beamspassing through the (1-1)th wavelength selection region 24 a and the(2-1)th wavelength selection region 34 a are different from each other,and the wavelength regions of the light beams passing through the(1-2)th wavelength selection region 24 b and the (2-2)th wavelengthselection region 34 b are different from each other. On the other hand,the (1-1)th wavelength selection region 24 a and the (2-2)th wavelengthselection region 34 b have a common passing wavelength region as awavelength region to pass the light beams, and the (1-2)th wavelengthselection region 24 b and the (2-1)th wavelength selection region 34 asimilarly have a common passing wavelength region as a wavelength regionto pass the light beams.

That is, there is such a relationship that the light beam of thewavelength that has passed through the (2-1)th wavelength selectionregion 34 a is shielded by the (1-1)th wavelength selection region 24 a.There is also such a relationship that the light beam of the wavelengththat has passed through the (2-1)th wavelength selection region 34 apasses through the (1-2)th wavelength selection region 24 b. There isalso such a relationship that the light beam of the wavelength that haspassed through the (2-2)th wavelength selection region 34 b is shieldedby the (1-2)th wavelength selection region 24 b. There is also such arelationship that the light beam of the wavelength that has passedthrough the (2-2)th wavelength selection region 34 b passes through the(1-1)th wavelength selection region 24 a.

The first wavelength selection portion 24 and the second wavelengthselection portion 34 have similar shapes. The similarity ratio isdetermined by the ratio of the focal length of the imaging opticalelement 22 and the focal length of the illumination lens 36. Forexample, if the focal length of the imaging optical element 22 is 100mm, and the focal length of the illumination lens 36 is 50 mm, thesimilarity ratio is two-fold. That is, the first wavelength selectionportion 24 is obtained by two-fold similar enlargement of the secondwavelength selection portion 34.

As described above, that the first wavelength selection portion 24 andthe second wavelength selection portion 34 have a similarityrelationship that these have similar shapes on predetermined crosssections, and also have a relationship concerning passing/shielding of aplurality of predetermined wavelengths in the regions of these meansthat the first wavelength selection portion 24 and the second wavelengthselection portion 34 have complementarity.

A processing device 16 is formed by, for example, a computer, andincludes a processor (processing circuit) and a non-transitory storagemedium. The processor includes one of a CPU (Central Processing Unit),an ASIC (Application Specific Integrated Circuit), a microcomputer, anFPGA (Field Programmable Gate Array), and a DSP (Digital SignalProcessor). In addition to a main storage device such as a memory, thenon-transitory storage medium can include an auxiliary storage device.As the non-transitory storage medium, a nonvolatile memory capable ofwriting and reading as needed, such as an HDD (Hard Disk Drive), an SSD(Solid State Drive), a magnetic disk, an optical disk (a CD-ROM, a CD-R,a DVD, or the like), a magnetooptical disk (an MO or the like), asemiconductor memory, or the like can be used.

In the processing device 16, only one processor and one storage mediummay be provided, or a plurality of processors and a plurality of storagemedia may be provided. In the processing device 16, the processorexecutes a program and the like stored in the non-transitory storagemedium, thereby performing processing. The program executed by theprocessor of the processing device 16 may be stored in a computer(server) connected to the processing device 16 via a network such as theInternet, or a server in a cloud environment. In this case, theprocessor downloads the program via the network. In the processingdevice 16, image acquisition from the image sensor 26 and various kindsof calculation processing based on the image acquired from the imagesensor 26 are executed by the processor and the like, and thenon-transitory storage medium functions as a data storage unit.

In addition, at least part of the processing of the processing device 16may be executed by a cloud server constituted in a cloud environment.The infrastructure of the cloud environment is formed by a virtualprocessor such as a virtual CPU and a cloud memory. In an example, imageacquisition from the image sensor 26 and various kinds of calculationprocessing based on the image acquired from the image sensor 26 areexecuted by the virtual processor, and the cloud memory functions as adata storage unit.

Note that in this embodiment, the processing device 16 controls theimage sensor 26. Also, the processing device 16 controls the lightsource 32.

Under the above-described configuration, the operation principle of theoptical inspection apparatus 10 according to this embodiment will bedescribed with reference to FIGS. 1, 4, and 5 .

The processing device 16 causes the light source 32 of the illuminationportion 14 to emit light, and the image sensor 26 captures an image(step S101).

Light from the light emitting point E of the light source 32 passesthrough the second wavelength selection portion 34, propagates along theoptical axis L2 of the illumination lens 36, and forms an image at theobject point O of the surface of the subject S via the beam splitter 38.Here, for example, a first light beam B1 is emitted from the lightemitting point E of the light source 32, passes through the (2-1)thwavelength selection region 34 a of the second wavelength selectionportion 34, passes through the illumination lens 36 as red lightincluding the first wavelength, is reflected by the beam splitter 38,and reaches the object point O of the subject S. Also, a second lightbeam B2 is emitted from the light emitting point E of the light source32, passes through the (2-2)th wavelength selection region 34 b of thesecond wavelength selection portion 34, passes through the illuminationlens 36 as blue light including the second wavelength, is reflected bythe beam splitter 38, and reaches the object point O of the subject S.

Note that the (2-1)th wavelength selection region 34 a of the secondwavelength selection portion 34 shields light of the second wavelengthdifferent from the first wavelength. For this reason, blue lightincluding the second wavelength is shielded by the (2-1)th wavelengthselection region 34 a of the second wavelength selection portion 34. The(2-2)th wavelength selection region 34 b of the second wavelengthselection portion 34 shields light of the first wavelength differentfrom the second wavelength. For this reason, red light including thefirst wavelength is shielded by the (2-2)th wavelength selection region34 b of the second wavelength selection portion 34.

In FIG. 1 , the standard surface of the subject S is, for example,substantially a mirror surface. This will be referred to as a standardsurface. At this time, a light beam that enters the object point O ofthe subject S is almost specularly reflected. That is, the BRDF at theobject point O includes the almost specular reflection component as themain component, and has a narrow direction distribution. On the otherhand, if an uneven defect C in a micron size exists at the object pointO, as shown in FIG. 4 , the BRDF at the object point O has a widedistribution. However, the uneven portion in the micron size may bedefined as the standard surface, and the mirror surface may be definedas the defect. That is, what kind of surface is defined as the standardsurface can arbitrary be determined.

As shown in FIG. 1 , of the light reflected at the object point O of thesurface of the subject S, the specular reflection component is reflectedin the specular reflection direction and directed to the imaging opticalelement (imaging lens) 22. For example, if the first light beam B1 isreflected at the object point O, the direction distribution of thereflected light of the first light beam B1 can be represented by a firstBRDF denoted by reference numeral 1. Of the reflected light that can berepresented by the first BRDF 1, the specular reflection componentpasses through the beam splitter 38, passes through the imaging opticalelement 22, and is shielded by the (1-1)th wavelength selection region24 a of the first wavelength selection portion 24. At this time, if thefirst wavelength selection portion 24 does not exist, the specularreflection component of the reflected light that can be represented bythe first BRDF 1 reaches an image point I on the image sensor 26.

Also, if the second light beam B2 is reflected at the object point O,the direction distribution of the reflected light of the second lightbeam B2 can be represented by a second BRDF denoted by reference numeral2. Of the reflected light that can be represented by the second BRDF 2,the specular reflection component passes through the beam splitter 38,passes through the imaging optical element (imaging lens) 22, and isshielded by the (1-2)th wavelength selection region 24 b of the firstwavelength selection portion 24. At this time, if the first wavelengthselection portion 24 does not exist, the specular reflection componentof the reflected light that can be represented by the second BRDF 2reaches the image point I on the image sensor 26.

As described above, since the first wavelength selection portion 24 andthe second wavelength selection portion 34 have complementarity, thespecular reflection component of the light reflected at the object pointO of the surface of the subject S (the first light beam B1 and thesecond light beam B2) is shielded without reaching the image sensor 26.That is, the image acquired by the image sensor 26 is an image that isblack as a whole, that is, the pixel values of the entire image aresubstantially 0. This means that the light emitted by the light source32 is not received by the image sensor 26.

Since the surface of the subject S is substantially a mirror surface,and the light beam that has entered the object point o is almostspecularly reflected, each of the first BRDF 1 and the second BRDF 2substantially mainly includes the specular reflection component, and thereflected light is substantially shielded by the first wavelengthselection portion 24. That is, the image acquired by the image sensor 26is an image that is black as a whole, that is, the pixel values of theentire image are substantially 0.

On the other hand, if the unevenness C exists at the object point o ofthe subject s, as shown in FIG. 4 , the BRDF at the object point orepresents a wide distribution as compared to the mirror-like surfacethat is the standard surface. That is, the first light beam B1 isreflected at the object point o, and changes to, for example, reflectedlight that can be represented by a third BRDF denoted by referencenumeral 3, and the second light beam B2 is reflected at the object pointo, and changes to, for example, reflected light that can be representedby a fourth BRDF denoted by reference numeral 4. In this case, in thefirst light beam B1, a component that is reflected at the object pointo, passes through the beam splitter 38 and the imaging optical element22, and reaches the (1-2)th wavelength selection region 24 b in additionto the (1-1)th wavelength selection region 24 a of the first wavelengthselection portion 24 is generated. The (1-2)th wavelength selectionregion 24 b passes the first light beam B1. The (component of the) firstlight beam B1 that has passed through the first wavelength selectionportion 24 reaches the image point I on the image sensor 26. Hence, thefirst wavelength is received at the image point I. That is, the sensor26 receives red light.

Similarly, in the second light beam B2, a component that is reflected atthe object point o, passes through the beam splitter 38 and the imagingoptical element 22, and reaches the (1-1)th wavelength selection region24 a in addition to the (1-2)th wavelength selection region 24 b of thefirst wavelength selection portion 24 is generated. The (1-1)thwavelength selection region 24 a passes the second light beam B2. The(component of the) second light beam B2 that has passed through thefirst wavelength selection portion 24 reaches the image point I on theimage sensor 26. Hence, the second wavelength is received at the imagepoint I. That is, the sensor 26 receives blue light.

As described above, the sensor 26 simultaneously receives the firstwavelength and the second wavelength for the object point o with theunevenness C, like the subject S shown in FIG. 4 . On the other hand, atthe image point I corresponding to the object point o on the standardsurface without the unevenness C, like the subject s shown in FIG. 1 ,the sensor 26 receives neither light components.

Concerning the image acquired by the image sensor 26, the processingdevice 16 judges whether the light from the surface of the subject S isreceived (step S102).

If the light from the surface of the subject s is received by the imagesensor 26 (YES in step S102), the processing device 16 determines thatthe unevenness C exists on the surface of the subject S (step S103). Ifthe light from the surface of the subject S is not received by the imagesensor 26 (NO in step S102), the processing device 16 determines thatthe unevenness C does not exist on the surface of the subject s (stepS104).

That is, the processing device (processor) 16 detects thepresence/absence of reception of reflected light from the subject s ineach pixel of the image sensor 26. Upon detecting the absence of lightreception in each pixel of the image sensor 26, the processing device(processor) 16 that the surface of the subject s for the image point Icorresponding to each pixel is the standard surface. Upon detecting thepresence of light reception, the processing device 16 outputs that thesurface of the subject S for the image point I is different from thestandard surface. Hence, in each pixel of the image sensor 26, theprocessing device 16 outputs the difference between the standard surfaceand the surface at the object point o corresponding to the pixel basedon the detection result of the presence/absence of light reception. Thatis, in each pixel of the image sensor 26, if the detection resultindicates the absence of light reception, the processing device 16outputs that the object point ◯ of the subject S corresponding to thepixel is on the standard surface. If the detection result indicates thepresence of light reception, the processing device 16 outputs that theobject point ◯ on the surface of the subject S corresponding to thepixel is on a surface different from the standard surface.

This allows the processing device 16 to identify the presence/absence ofthe unevenness C on the subject s from the image acquired by the imagesensor 26. If the unevenness C exists on the subject S, the sensor 26can receive not only the light of the first wavelength but also thelight of the second wavelength at the same time. For this reason, theS/N ratio of the light received by the sensor 26 can be increased. Onthe other hand, if the sensor 26 receives only the first wavelength (redlight) or only the second wavelength (blue light), the light amountdecreases as compared to a case where both the first wavelength and thesecond wavelength are received. Hence, the S/N ratio lowers as comparedto the case where both are received. That is, in all pixels of the imagecaptured by the image sensor 26, the processing device 16 obtains darkblack at a position where no light is received and a bright color thatis a mixture of red light and blue light at a position where light isreceived. For this reason, the processing device 16 can output positionswhere the unevenness C exists and positions where the unevenness C doesnot exist with a clear contrast. That is, these can be expressed with aclear contrast not only by brightness but also by different colors.

In this embodiment, an example in which two different wavelengths, thattis, the first wavelength and the second wavelength are used, has beendescribed. Note that the image sensor 26 functions even withoutdiscrimination between the two wavelengths. That is, substantially, theprocessing device 16 can judge that the unevenness C does not exist atthe object point o on the subject S for which the pixel value at theimage point I is 0, and that the unevenness C exists at a position wherethe pixel value is larger than 0. Hence, the sensor 26 can use amonochrome sensor. Also, since the sensor 26 may use a color sensor, therange of choice for usable image sensors can be expanded.

Also, in this embodiment, the standard surface is a mirror surface.However, the standard surface may be an uneven surface. In this case aswell, since the BRDF on the standard surface and the BRDF on a surfaceare different from each other, two complementary wavelength selectionportions can similarly be made to function by appropriately adjustingthese. Hence, in each pixel of the image sensor 26, the processingdevice 16 outputs the difference between the standard surface and thesurface at the object point o corresponding to the pixel based on thedetection result of the presence/absence of light reception. That is, ineach pixel of the image sensor 26, if the detection result indicates theabsence of light reception, the processing device 16 outputs that theobject point o of the subject S corresponding to the pixel is on asurface different from the standard surface. If the detection resultindicates the presence of light reception, the processing device 16outputs that the object point ◯ on the surface of the subject Scorresponding to the pixel is on the standard surface. Thepresence/absence of light reception in each pixel of the image sensor 26and whether the object point is on the standard surface canappropriately be set.

In this embodiment, the imaging optical element 22 and the illuminationlens 36 can be made common. That is, one imaging optical element 22 maybe used as the illumination lens 36. In this case, the beam splitter 38is arranged on a side closer to the image sensor 26 than the imagingoptical element 22. In this case, since the imaging optical element 22and the illumination lens 36 are common (single), focal lengths thereofequal.

In this embodiment, the ratio of the total area of the light receivingsurface of the image sensor 26 to the total area of the light emittingsurface of the light source 32 can be adjusted by the focal length ofthe imaging optical element 22 or the illumination lens 36. That is, forexample, the area of the image sensor 26 can be adjusted by adjustingthe position of the imaging optical element 22 or the illumination lens36 with respect to the light source 32 having an arbitrary lightemitting surface.

Also, the beam splitter 38 may be a polarization beam splitter 38. Inthis case, only a component whose direction of polarization is rotatedby scattering from the surface of the subject s is received by the imagesensor 26. This can increase the sensitivity to scattering.

The first wavelength selection portion 24 according to this embodimentis provided in the optical path between the subject S and the imagingportion 12 on the optical axis L1 of the imaging portion 12, andselectively passes a plurality of light components of predeterminedwavelengths. The second wavelength selection portion 34 is provided inthe optical path between the illumination portion 14 (light source 32)and the subject S on the optical axis L2 of the illumination portion 14,and selectively passes a plurality of light components of predeterminedwavelengths in a state with complementarity to the first wavelengthselection portion 24. Hence, if the image sensor 26 of the imagingportion 12 receives light from the surface of the subject S, the opticalinspection apparatus 10 detects the presence of the unevenness C on thesurface of the subject s. If the image sensor 26 of the imaging portion12 does not receive light from the surface of the subject s, the opticalinspection apparatus 10 detects the absence of the unevenness C on thesurface of the subject S. The surface state of the subject S can bejudged based on the presence/absence of light reception, and theaccuracy of optical inspection of the surface of the subject S can beincreased. Hence, according to this embodiment, it is possible toprovide the optical inspection apparatus 10 capable of increasing theaccuracy of optical inspection of the surface of the subject s, theprocessing device 16, an optical inspection method, and a non-transitorystorage medium storing an optical inspection program.

Modification

If a color sensor is used as the image sensor 26 in place of amonochrome sensor, the image sensor 26 can identify blue light and redlight in each pixel. In this case, for example, if the uneven portion Cexists at the object point o, and the image sensor 26 receives only bluelight that is the second light beam, this means that the BRDF of redlight that is the first light beam and the BRDF of blue light that isthe second light beam are different. In this case, it means that thedistribution of the BRDF of blue light that is the second light beam iswider than the distribution of the BRDF of red light that is the firstlight beam. That is, the incidence angle dependence of the BRDF can begrasped. Since this makes it possible to acquire more detailed BRDFinformation, more accurate optical inspection can be performed.

As the first wavelength selection portion 24 and the second wavelengthselection portion 34, various units can be used. For example, the firstwavelength selection portion 24 and the second wavelength selectionportion 34 impart anisotropy around the optical axes L1 and L2 of theoptical inspection apparatus 10, thereby identifying the direction ofthe tilt of the surface of the subject s. In this case, the image sensor26 is a color sensor capable of identifying at least two differentcolors. It is assumed here that the image sensor 26 can identify thefirst wavelength (red) and the second wavelength (blue). For example, asshown in FIG. 6 , the (1-1)th wavelength selection region 24 a and the(1-2)th wavelength selection region 24 b are provided as the firstwavelength selection portion 24. The second wavelength selection portion34 has complementarity to the (1-1)th wavelength selection region 24 aand the (1-2)th wavelength selection region 24 b of the first wavelengthselection portion 24, and these are the (2-1)th wavelength selectionregion 34 a and the(2-2)th wavelength selection region 34 b. Inaddition, the first wavelength selection portion 24 includes awavelength shielding portion 25 around the (1-1)th wavelength selectionregion 24 a and the (1-2)th wavelength selection region 24 b. Thewavelength shielding portion 25 shields all light beams emitted from thelight source 32.

Note that in FIG. 6 , each of the (1-1)th wavelength selection region 24a and the (1-2)th wavelength selection region 24 b of the firstwavelength selection portion 24 has a semicircular shape, and when the(1-1)th wavelength selection region 24 a and the (1-2)th wavelengthselection region 24 b are combined, a circular shape is obtained.Although not illustrated, the (2-1)th wavelength selection region 34 aof the second wavelength selection portion 34 has a semicircular shape,like the (1-1)th wavelength selection region 24 a of the firstwavelength selection portion 24, and the (2-2)th wavelength selectionregion 34 b of the second wavelength selection portion 34 has asemicircular shape, like the (1-2)th wavelength selection region 24 b ofthe first wavelength selection portion 24. The direction to arrangethese adjacently is the same directions along the optical axes L1 andL2.

At this time, if the surface of the subject S has a tilt D, as shown inFIG. 7 , the first BRDF 1 and the second BRDF 2 also tilt in the samedirection. Accordingly, the first light beam B1 reaches the (1-2)thwavelength selection region 24 b of the first wavelength selectionportion 24 and the wavelength shielding portion 25, and passes the(1-2)th wavelength selection region 24 b. For this reason, the imagesensor 26 receives the first wavelength by the red channel. On the otherhand, the second light beam B2 reaches the (1-2)th wavelength selectionregion 24 b of the first wavelength selection portion 24 and thewavelength shielding portion 25 and is shielded there. That is, theimage sensor 26 does not receive the light of the second wavelength. Forthis reason, the signal (pixel value) of the blue channel is 0. Assumethat the direction of the tilt D at the object point o is reverse tothat shown in FIG. 7 . In this case, only the blue light that is thelight of the second wavelength is received by the image sensor 26 by thesame mechanism. Thus, when the color image sensor 26 and the firstwavelength selection portion 24 that imparts anisotropy around theoptical axis L1 are used, the direction of the tilt can be estimated byidentifying whether blue light is received or red light is received.That is, if reflected light from the subject s is received in at leastone pixel of the image sensor 26, the processing device (processor) 16identifies the tilting direction of the surface at the object point ocorresponding to the pixel based on the color of the received light.

Each of the wavelength selection portions 24 and 34 is suitablysupported by, for example, a support portion. The support portions canindividually or synchronously rotate the wavelength selection portions24 and 34 by, for example, an equal angle. Even if the BRDF has specialanisotropy, an accurate BRDF distribution can be acquired, by capturingan image by the image sensor 26 while rotating the wavelength selectionportions 24 and 34.

When the first wavelength selection portion 24 and the second wavelengthselection portion 34, which maintain a complementary relationship, arerotated about the optical axes L1 and L2 by an appropriate angle, forexample, 45°, and an image is acquired, the direction of the tilt D atthe object point o of the subject s can be estimated.

Thus, when the color image sensor 26 and the first wavelength selectionportion 24 that imparts anisotropy around the optical axis L1 are used,the direction of the tilt of the surface of the subject S can beestimated by identifying whether blue light is received or red light isreceived.

According to this modification, it is possible to provide the opticalinspection apparatus 10 capable of increasing the accuracy of opticalinspection of the surface of the subject s, the processing device 16, anoptical inspection method, and a non-transitory storage medium storingan optical inspection program.

Examples of Wavelength Selection Portions

FIGS. S. 8 to 12 shows various shapes of the first wavelength selectionportion 24. The wavelength selection portion 24 can be optimized inaccordance with the sensitivity necessary for optical inspection.Although not illustrated, as the second wavelength selection portion 34,a portion that maintains the complementary relationship with the firstwavelength selection portion 24 is used.

The (1-1)th wavelength selection region 24 a of the first wavelengthselection portion 24 shown in FIG. 8 is formed at a position except aspiral, and the (1-2)th wavelength selection region 24 b is formed atthe position of the spiral. Although not illustrated, the (2-1)thwavelength selection region 34 a of the second wavelength selectionportion 34 is formed in a shape similar to the (1-1)th wavelengthselection region 24 a at the position except the spiral in FIG. 8 , andthe (2-2)th wavelength selection region 34 b is formed in a shapesimilar to the (1-2)th wavelength selection region 24 b at the positionof the spiral in FIG. 8 .

The wavelength selection portion 24 shown in FIG. 9 and the wavelengthselection portion 34 (not shown) are arranged in the same relationshipas the wavelength selection portion 24 shown in FIG. 2 and thewavelength selection portion 34 shown in FIG. 3 . In FIG. 9 , the(1-1)th wavelength selection region 24 a of the first wavelengthselection portion 24 is formed at a position except a ring, and the(1-2)th wavelength selection region 24 b is formed at the position ofthe ring.

The first wavelength selection portion 24 shown in FIG. 10 includes fourwavelength selection regions 24 a, 24 b, 24 c, and 24 d. The wavelengthselection portion 24 shown in FIG. 10 and the wavelength selectionportion 34 (not shown) are arranged in the same relationship as thewavelength selection portion 24 shown in FIG. 2 and the wavelengthselection portion 34 shown in FIG. 3 . Although not illustrated, thesecond wavelength selection portion 34 includes four wavelengthselection regions 34 a, 34 b, 34 c, and 34 d. Note that the firstwavelength selection portion 24 shown in FIG. 10 has anisotropy. Hence,the first wavelength selection portion 24 shown in FIG. 10 can be usedto detect the above-described tilting surface D (see FIG. 7 ).

The (1-1)th wavelength selection region 24 a passes, for example, thefirst wavelength, and shields the second to fourth wavelengths that aredifferent. The (1-2)th wavelength selection region 24 b passes, forexample, the second wavelength, and shields the first, third, and fourthwavelengths that are different. The (1-3)th wavelength selection region24 c passes, for example, the third wavelength, and shields the first,second, and fourth wavelengths that are different. The (1-4)thwavelength selection region 24 d passes, for example, the fourthwavelength, and shields the first to third wavelengths that aredifferent.

Which wavelength is to be passed and which wavelength is to be shieldedby each of the wavelength selection regions 34 a, 34 b, 34 c, and 34 dof the second wavelength selection portion 34 can appropriately be set.The (2-1)th wavelength selection region 34 a passes, for example, thefourth wavelength, and shields the first to third wavelengths that aredifferent. The (2-2)th wavelength selection region 34 b passes, forexample, the first wavelength, and shields the second to fourthwavelengths that are different. The (2-3)th wavelength selection region34 c passes, for example, the second wavelength, and shields the first,third, and fourth wavelengths that are different. The (2-4)th wavelengthselection region 34 d passes, for example, the third wavelength, andshields the first, second, and fourth wavelengths that are different.

The wavelength selection portion 24 shown in FIG. 11 and the wavelengthselection portion 34 (not shown) are arranged in the same relationshipas the wavelength selection portion 24 shown in FIG. 2 and thewavelength selection portion 34 shown in FIG. 3 .

The first wavelength selection portion 24 shown in FIG. 11 includes twowavelength selection regions 24 a and 24 b. The wavelength selectionregions 24 a and 24 b each have a stripe shape and are adjacent in theup-and-down direction shown in FIG. 11 . Note that the first wavelengthselection portion 24 shown in FIG. 11 has anisotropy. Hence, the firstwavelength selection portion 24 shown in FIG. 11 can be used to detectthe above-described tilting surface D.

The wavelength selection portion 24 shown in FIG. 12 and the wavelengthselection portion 34 (not shown) are arranged in the same relationshipas the wavelength selection portion 24 shown in FIG. 2 and thewavelength selection portion 34 shown in FIG. 3 .

The first wavelength selection portion 24 shown in FIG. 12 includesthree wavelength selection regions 24 a and 24 b. The (1-1)th wavelengthselection region 24 a is disposed between the (1-2)th wavelengthselection regions 24 b.

Second Embodiment

An optical inspection apparatus 10 according to this embodiment will bedescribed in detail with reference to FIG. 13 . The optical inspectionapparatus 10 according to this embodiment is basically the same as theoptical inspection apparatus according to the first embodiment.Differences will be described below.

In this embodiment, an image sensor 26 is not a monochrome sensor but acolor sensor capable of discriminating between blue light, green light,and red light.

A first wavelength selection portion 24 and a second wavelengthselection portion 34 have a complementary relationship with respect tooptical axes L1 and L2. The first wavelength selection portion 24includes a (1-1)th wavelength selection region 24 a, a (1-2)thwavelength selection region 24 b, and a (1-3)th wavelength selectionregion 24 c. The wavelength spectra of light passing through thewavelength selection regions 24 a, 24 b, and 24 c are different fromeach other. The second wavelength selection portion 34 includes a(2-1)th wavelength selection region 34 a, a (2-2)th wavelength selectionregion 34 b, and a (2-3)th wavelength selection region 34 c. Thewavelength spectra of light passing through the wavelength selectionregions 34 a, 34 b, and 34 c are different from each other.

The operation principle of the optical inspection apparatus 10 accordingto this embodiment will be described.

Light that is emitted from a light emitting point E on the lightemitting surface of a light source 32 and passes through the (2-3)thwavelength selection region 34 c changes to a third light beam B3including a wavelength of 550 nm and becomes green light. The thirdlight beam B3 passes through an illumination lens 36, is reflected by abeam splitter 38, and reaches an object point o. The third light beam B3is further reflected at the object point o, changes to reflected lightthat can be represented by a third BRDF denoted by reference numeral 3,passes through the beam splitter 38, passes through an imaging lens 22,and reaches the first wavelength selection portion 24.

If the surface of a subject s is a mirror surface, the first light beamB1, the second light beam B2, and the third light beam B3 are shieldedby the first wavelength selection portion 24. In this case, the imagesensor 26 receives no light at the image point on the image sensor 26.That is, a dark image (pixel value = 0) is obtained. At this time, noneof blue light, red light, and green light is received at an image pointI on the image sensor 26, and the number of colors of received light is0. This is defined as the number of colors = 0.

On the other hand, if unevenness C exists at the object point o, thefirst light beam B1, the second light beam B2, and the third light beamB3 pass through the first wavelength selection portion 24. For thisreason, the image sensor 26 receives light of three colors, that is,blue light, red light, and green light at the image point I on the imagesensor 26. This is defined as the number of colors = 3. A processingdevice 16 acquires the image from the image sensor 26, and outputs thenumber of colors in each pixel. Hence, the processing device 16 canrecognize whether, in each pixel, light has passed through the threewavelength selection regions 24 a, 24 b, and 24 c of the firstwavelength selection portion 24.

The number of colors depends on the extent of the distribution of theBRDF at the object point o. That is, the wider the distribution of theBRDF is, the larger the number of colors detected by the processingdevice 16 is. The narrower the distribution of the BRDF is, the smallerthe number of colors detected by the processing device 16 is. In otherwords, it is considered that the larger the number of colors is, thewider the scattered light distribution (BRDF) is, and the smaller thenumber of colors is, the narrower the scattered light distribution(BRDF) is. Hence, if the number of colors at each image point I can beacquired by color count estimation processing of the processing device16, the difference of the BRDF at each object point o can be identified.That is, the processing device (processor) 16 identifies the differenceof the surface state based on the number of colors of received light.For example, if reflected light from the subject S is received in atleast one pixel of the image sensor 26, the processing device(processor) 16 recognizes that the surface at the object point ocorresponding to the pixel is different from the standard surface.

However, as for how the processing device 16 counts the number ofcolors, various methods can be considered depending on the manner to setbackground noise (dark current noise or the spectral performance of thesensor or wavelength selection regions). For example, depending on thespectral performance of the sensor 26, even if green light does notreach the sensor 26, an electrical signal corresponding to green lightmay react by red light. To prevent this, calibration for associating thenumber of colors with the number of wavelength selection portions 24 and34 through which light beams have passed is performed by offsettingbackground noise. By this calibration, the processing device 16 canacquire the correct number of colors.

Since the BRDF has correlation with surface properties/shape, theoptical inspection apparatus 10 according to this embodiment canidentify the difference of the surface state at each object point O onthe surface of the subject s.

According to this embodiment, it is possible to provide the opticalinspection apparatus 10 capable of increasing the accuracy of opticalinspection of the surface of the subject s, the processing device 16, anoptical inspection method, and a non-transitory storage medium storingan optical inspection program.

Third Embodiment

An optical inspection apparatus 10 according to this embodiment will bedescribed in detail with reference to FIG. 14 . The optical inspectionapparatus 10 according to this embodiment is basically the same as theoptical inspection apparatus according to the first embodiment.Differences will be described below.

In this embodiment, a second wavelength selection portion 34 furtherincludes, for example, a band-shaped wavelength shielding portion 35, asshown in FIGS. 14 and 15 .

A width (line width) W of the band of the wavelength shielding portion35 shown in FIG. 15 is defined as a shielding width.

Assume that the standard surface of a subject s shown in FIG. 14 is amirror surface, and a BRDF at an object point ◯ on the standard surfaceincludes only a specular reflection component. At this time, in a casewhere the shielding width W shown in FIG. 15 is 0 (the wavelengthshielding portion 35 is absent), if the BRDF spreads due to the presenceof unevenness C on the surface of the subject s, or the like, lightreception occurs immediately in an image sensor 26. That is, it can besaid that if the shielding width W is 0 (the wavelength shieldingportion 35 is absent), the sensitivity to the difference of thedistribution of the BRDF is very high. On the other hand, when theshielding width W shown in FIG. 15 is increased, a state in which nolight beam passing through a first wavelength selection portion 24exists even if the BRDF spreads a little can be implemented. That is,the sensitivity to the difference of the distribution of the BRDF can belowered. The advantage is that, for example, if the standard surface ofthe subject S has a little diffusibility, and the BRDF spreads a little,light reception of reflected light from the standard surface cancompletely be shielded, and the S/N ratio can be increased. As describedabove, when the second wavelength selection portion 34 includes thewavelength shielding portion 35, and the shielding width W of thewavelength shielding portion 35 can be adjusted, the sensitivity to thedifference of the BRDF can be adjusted.

According to the optical inspection apparatus 10 of this embodiment,since the second wavelength selection portion 34 includes the wavelengthshielding portion 35, and the shielding width W is adjusted inaccordance with the BRDF, the S/N ratio of detection of a defect such asthe unevenness C on the surface of the subject s can be adjusted.

Note that when the shielding width W of the shielding portion 35 iselectromagnetically adjusted, the number of lineups of the secondwavelength selection portion 34 can be decreased.

In this embodiment, an example in which the second wavelength selectionportion 34 includes the shielding portion 35 has been described. Ashielding portion corresponding to the shielding portion 35 may beprovided between a first wavelength selection region 24 a and a secondwavelength selection region 24 b of the first wavelength selectionportion 24. In this case, the shielding portion 35 may be absent.

According to this embodiment, it is possible to provide the opticalinspection apparatus 10 capable of increasing the accuracy of opticalinspection of the surface of the subject S, a processing device 16, anoptical inspection method, and a non-transitory storage medium storingan optical inspection program.

Fourth Embodiment

An optical inspection apparatus 10 according to this embodiment will bedescribed in detail with reference to FIG. 16 . This embodiment isbasically the same as the optical inspection apparatus 10 according tothe first embodiment. Differences will be described below.

A light source 32 of an illumination portion 14 is an LED. Theillumination portion 14 includes a pinhole opening 40 on a focal planeF2 of an illumination lens 36. The hole diameter of the pinhole opening40 is, for example, 0.4 mm. With this configuration, the illuminationportion 14 can irradiate a subject with parallel light. The parallellight passes through a second wavelength selection portion 34, and thesurface of a subject S is irradiated with the beam via a beam splitter38.

Note that the second wavelength selection portion 34 of the opticalinspection apparatus 10 according to this embodiment is arranged on theoptical path on a side closer to the subject S than the illuminationlens 36. The arrangement of the second wavelength selection portion 34is the same as the arrangement of the second wavelength selectionportion 34 of the optical inspection apparatus 10 according to thesecond embodiment (see FIG. 13 ).

A first wavelength selection portion 24 of the optical inspectionapparatus 10 according to this embodiment is arranged between an imagingportion 12 and the subject s. The first wavelength selection portion 24is arranged on a side closer to the subject S than the imaging lens 22.That is, the first wavelength selection portion 24 is arranged in aplace that is not the focal plane of the imaging lens 22. Thearrangement of the first wavelength selection portion 24 is differentfrom the arrangement of the first wavelength selection portion 24 of theoptical inspection apparatus 10 according to the second embodiment (seeFIG. 13 ). The arrangement of the first wavelength selection portion 24on a cross section shown in FIG. 16 is reversed in the left-and-rightdirection from the arrangement of the first wavelength selection portion24 on the cross section shown in FIG. 13 . The first wavelengthselection portion 24 and the second wavelength selection portion 34 arecomplementary to each other.

The operation principle of the optical inspection apparatus 10 accordingto this embodiment will be described.

Assume that the standard surface on the surface of the subject s is amirror surface. According to this embodiment, light reflected by thestandard surface is wholly shielded by the first wavelength selectionportion 24. This is because the first wavelength selection portion 24and the second wavelength selection portion 34 are complementary to eachother.

A case where an uneven shape C (see FIG. 16 ) exists at an object pointO on the surface of the subject s will be considered. A BRDF 1 at theobject point O on the surface of the subject s represents a distributionwider than that on the standard surface. This generates light thatpasses through the first wavelength selection portion 24, and an imagesensor 26 receives the light that passes through the first wavelengthselection portion 24.

Thus, according to the optical inspection apparatus 10 of thisembodiment, it is possible to implement optical inspection with a highS/N ratio for the unevenness C. In this embodiment, the first wavelengthselection portion 24 can be arranged afterwards before a commerciallyavailable camera in which an imaging lens 22 and the image sensor 26 areintegrated. This can obtain an advantage that the versatility of theoptical inspection apparatus 10 can be enhanced.

According to this embodiment, it is possible to provide the opticalinspection apparatus 10 capable of increasing the accuracy of opticalinspection of the surface of the subject S, a processing device 16, anoptical inspection method, and a non-transitory storage medium storingan optical inspection program.

Fifth Embodiment

An optical inspection apparatus 10 according to this embodiment will bedescribed in detail with reference to FIG. 17 . The optical inspectionapparatus 10 according to this embodiment is basically the same as theoptical inspection apparatus according to the fourth embodiment.Differences will be described below.

FIG. 17 is a perspective view of the optical inspection apparatus 10according to this embodiment.

An illumination portion 14 includes a light source (LED) 32, an opening40 (see FIG. 16 ), an illumination lens 36 (see FIG. 16 ), and a secondwavelength selection portion 34. The opening 40 has a slit shape. Here,for example, the slit width is 0.4 mm, and the length is 300 mm in thelongitudinal direction. As the light source 32, for example, a pluralityof light sources each having a light emitting surface of 1.0 mm × 3.0 mmare arranged along the longitudinal direction of the slit of the opening40. The illumination lens 36 is a cylindrical lens, and is 300 mm longin the longitudinal direction. The focal length is, for example, 50 mm.The slit-shaped opening 40 is arranged on a focal plane F2 of theillumination lens 36. With this configuration, light from theillumination portion 14 forms a line beam. For this reason, the lightfrom the illumination portion 14 changes to parallel light on a firstcross section S1 orthogonal to the slit-shaped opening 40. On the otherhand, the light from the illumination portion 14 changes to diffusedlight in a light beam orthographically projected to a second crosssection S2 orthogonal to the first cross section S1.

A first wavelength selection portion 24 and the second wavelengthselection portion 34 are each formed into a stripe shape and arecomplementary to each other.

The illumination portion 14 and an imaging portion 12 are arranged suchthat an optical axis L2 of the illumination lens of the illuminationportion 14 and an optical axis L2 of an imaging lens 22 hold apositional relationship of specular reflection with respect to thesurface (subject) of a subject S. Note that a beam splitter 38 is notused here.

In FIG. 17 , the first cross section S1 includes the optical axes L1 andL2, and the light from the illumination portion 14 is parallel light. Onthe other hand, a cross section orthogonal to the first cross section S1is defined as the second cross section S2. In the light beamorthographically projected to the second cross section S2, the lightfrom the illumination portion 14 is not the parallel light but diffusedlight.

The first wavelength selection portion 24 includes three wavelengthselection regions 24 a, 24 b, and 24 c, and the second wavelengthselection portion 34 includes three wavelength selection regions 34 a,34 b, and 34 c. The wavelength selection regions 24 a, 24 b, 24 c, 34 a,34 b, and 34 c each have a stripe shape.

On the first cross section S1 or a cross section parallel to that, theplurality of wavelength selection regions 24 a, 24 b, and 24 c of thefirst wavelength selection portion 24 and the plurality of wavelengthselection regions 34 a, 34 b, and 34 c of the second wavelengthselection portion 34 are arranged. That is, on the first cross sectionS1, the direction of arraying the plurality of wavelength selectionregions 24 a, 24 b, 24 c, 34 a, 34 b, and 34 c is included. On the otherhand, on the second cross section S2 orthogonal to the first crosssection S1 or a cross section parallel to that, the plurality ofwavelength selection regions 24 a, 24 b, 24 c, 34 a, 34 b, and 34 c donot change.

The illumination portion 14 irradiates the surface of the subject S toform an irradiation field F in which the color changes in a stripepattern.

On the first cross section S1, the spread of the distribution of a BRDF1 can be identified by the number of colors of light that has passedthrough the wavelength selection regions 24 a, 24 b, and 24 c of thewavelength selection portion 24. Since the light from the illuminationportion 14 is parallel light, the angle of view in a directioncorresponding to the cross section S1 is narrow in the imaging portion12. That is, the imaging range in this direction is narrow. On the otherhand, on the second cross section S2 or a cross section parallel tothat, the number of colors is constant. This is because, on the crosssection S2 or a cross section parallel to that, the wavelength selectionregions 24 a, 24 b, and 24 c of the first wavelength selection portion24 and the wavelength selection regions 34 a, 34 b, and 34 c of thesecond wavelength selection portion 34 do not change. Since the lightfrom the illumination portion 14 is diffused light in the light beamorthographically projected to the cross section S2, the angle of view ina direction corresponding to the cross section S2 is wide in an imageacquired by the imaging portion 12. Thus, in the acquired image, theangle of view is narrow in one of two directions orthogonal to theoptical axes L1 and L2, but can be made wide in the direction orthogonalto that. Also, the number of colors at an image point I is the number ofwavelength selection regions 24 a, 24 b, and 24 c when the light beampasses through the wavelength selection portion 24 on the first crosssection S1.

With these, as compared to a case where the light from the illuminationportion 14 is completely changed to parallel light, the angle of viewcan be made wide as a whole. Also, since the wavelength selectionregions are each formed into a stripe shape, the angle of view can bemade wide as a whole as compared to the otherwise case.

In addition, like the optical inspection apparatus 10 according to thefourth embodiment (see FIG. 16 ), since the first wavelength selectionportion 24 is arranged in front of the imaging portion 12, the opticalsystem can be constructed for any imaging portion (that is, the camera)12. That is, the range of choice for the camera can be expanded by thisconfiguration. That is, since the light that has passed through thewavelength selection portion 24 passes through the imaging lens 22 forimage capturing, the wavelength selection portion 24 can easily bearranged.

According to this embodiment, it is possible to provide the opticalinspection apparatus 10 capable of increasing the accuracy of opticalinspection of the surface of the subject S, a processing device 16, anoptical inspection method, and a non-transitory storage medium storingan optical inspection program.

According to at least one of the above-described embodiments, it ispossible to provide the optical inspection apparatus 10 capable ofincreasing the accuracy of optical inspection of the surface of thesubject s, the processing device 16, an optical inspection method, and anon-transitory storage medium storing an optical inspection program.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel embodiments described hereinmay be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the embodimentsdescribed herein may be made without departing from the spirit of theinventions. The accompanying claims and their equivalents are intendedto cover such forms or modifications as would fall within the scope andspirit of the inventions.

What is claimed is:
 1. An optical inspection apparatus comprising: animaging portion including an image sensor configured to capture asubject by light from the subject; a first wavelength selection portionprovided on an optical axis of the imaging portion and configured toselectively pass a plurality of light components of predeterminedwavelengths; an illumination portion configured to illuminate thesubject; and a second wavelength selection portion provided on anoptical axis of the illumination portion and configured to pass theplurality of light components of the predetermined wavelengthscomplementarily to the first wavelength selection portion.
 2. Theapparatus according to claim 1, wherein the first wavelength selectionportion comprises: a (1-1)th region configured to shield light of afirst wavelength and pass light of a second wavelength different fromthe first wavelength toward the image sensor, and a (1-2)th regionconfigured to pass the light of the first wavelength toward the imagesensor and shield the light of the second wavelength, and the secondwavelength selection portion comprises: a (2-1)th region having a shapesimilar to the (1-1)th region and configured to pass the light of thefirst wavelength toward the subject and shield the light of the secondwavelength, and a (2-2)th region having a shape similar to the (1-2)thregion and configured to pass the light of the second wavelength towardthe subject and shield the light of the first wavelength.
 3. Theapparatus according to claim 1, wherein at least one of the firstwavelength selection portion and the second wavelength selection portionincludes a wavelength shielding portion.
 4. The apparatus according toclaim 3, wherein the wavelength shielding portion has a band shape, awidth of the band is defined as a shielding width, and the shieldingwidth is configured to be adjusted.
 5. The apparatus according to claim1, wherein the imaging portion comprises a first imaging opticalelement, the illumination portion comprises a second imaging opticalelement, the first wavelength selection portion is arranged on a focalplane of the first imaging optical element, and has anisotropy to theoptical axis of the imaging portion, and the second wavelength selectionportion is arranged on a focal plane of the second imaging opticalelement, and has anisotropy to the optical axis of the illuminationportion.
 6. The apparatus according to claim 1, wherein the imagingportion comprises a first imaging optical element, the first wavelengthselection portion is arranged on or near a focal plane of the firstimaging optical element of the imaging portion, the illumination portioncomprises a second imaging optical element, and the second wavelengthselection portion is arranged on or near a focal plane of the secondimaging optical element of the illumination portion.
 7. The apparatusaccording to claim 1, wherein the illumination portion is configured toirradiate the subject with parallel light, and the first wavelengthselection portion is arranged between the imaging portion and thesubject.
 8. The apparatus according to claim 1, further comprising abeam splitter between the subject and the imaging portion, and the beamsplitter is a polarization beam splitter.
 9. A processing devicecomprising: a processor configured to: detect, in each pixel of theimage sensor of the optical inspection apparatus defined in claim 1,presence/absence of light reception of reflected light from the subject,and in each pixel of the image sensor, if the detection result indicatesthe absence of light reception, output that an object point of thesubject corresponding to the pixel is on a standard surface, and if thedetection result indicates the presence of light reception, output thatthe object point on a surface of the subject corresponding to the pixelis on a surface different from the standard surface.
 10. A processingdevice comprising: a processor configured to: detect, in each pixel ofthe image sensor of the optical inspection apparatus defined in claim 1,presence/absence of light reception of reflected light from the subject,and in each pixel of the image sensor, if the detection result indicatesthe absence of light reception, output that an object point of thesubject corresponding to the pixel is on a surface different from astandard surface, and if the detection result indicates the presence oflight reception, output that the object point on a surface of thesubject corresponding to the pixel is on the standard surface.
 11. Anoptical inspection method of inspecting a surface of a subject using anoptical inspection apparatus defined in claim 1, the method comprising:detecting, in each pixel of the image sensor, presence/absence of lightreception of reflected light from the subject; and outputting, in eachpixel of the image sensor, a difference between a standard surface and asurface at an object point corresponding to the pixel based on adetection result of the presence/absence of light reception.
 12. Themethod according to claim 11, wherein a difference of a surface state isidentified based on the number of colors of light received in a leastone pixel of the image sensor.
 13. A non-transitory storage mediumstoring an optical inspection program configured to inspect a surface ofa subject using an optical inspection apparatus defined in claim 1, theoptical inspection program causing a computer to execute: processing ofdetecting, in each pixel of the image sensor, presence/absence of lightreception of reflected light from the subject; and processing ofoutputting, in each pixel of the image sensor, a difference between astandard surface and a surface at an object point corresponding to thepixel based on a detection result of the presence/absence of lightreception.